How to scale same material on two different objects separately without affecting the other?
If you have to use the same material, the most straightforward way would be to use the UV texture space,and give each object a UV map with its own transform (including scale)... but this is a 2D space.. (below)





For 3D, you can use the Generated texture space, and manipulating that on the objects, using ShiftT > S (optionally constraining withXY or Z). (below)



Or, you can use the objects' Pass Indices (set in the Object Properties > Relations panel) to discriminate between objects. In the node tree, That number can be picked up using an Object Info node > Object Index, and used any way you like.